Method and apparatus for block partition with non-uniform quad split

ABSTRACT

A method of video decoding includes acquiring a current picture and signaling information from a coded video bitstream. The method further includes determining, from the signaling information, whether the block is partitioned in accordance with a quad split partition type. The method further includes, in response to determining that the block is not partitioned in accordance with the quad split partition type, determining whether the block is partitioned in accordance with a split partition type. The method further includes in response to determining that the block is partitioned in accordance with the split partition type, determining whether the block is partitioned in accordance with a non-uniform quad split partition type in which the block is partitioned into four sub-blocks along a same direction. The method further includes in response to determining that the block is partitioned in accordance with the non-uniform quad split partition type, reconstructing the block.

INCORPORATION BY REFERENCE

This present disclosure claims the benefit of priority to U.S.Provisional Application No. 62/695,390, “BLOCK PARTITION WITHNON-UNIFORM QUAD-SPLIT” filed on Jul. 9, 2018, which is incorporated byreference herein in its entirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Video coding and decoding using inter-picture prediction with motioncompensation has been known for decades. Uncompressed digital video caninclude a series of pictures, each picture having a spatial dimensionof, for example, 1920×1080 luminance samples and associated chrominancesamples. The series of pictures can have a fixed or variable picturerate (informally also known as frame rate), of, for example 60 picturesper second or 60 Hz. Uncompressed video has significant bitraterequirements. For example, 1080p60 4:2:0 video at 8 bit per sample(1920×1080 luminance sample resolution at 60 Hz frame rate) requiresclose to 1.5 Gbit/s bandwidth. An hour of such video requires more than600 GByte of storage space.

One purpose of video coding and decoding can be the reduction ofredundancy in the input video signal, through compression. Compressioncan help reduce aforementioned bandwidth or storage space requirements,in some cases by two orders of magnitude or more. Both lossless andlossy compression, as well as a combination thereof can be employed.Lossless compression refers to techniques where an exact copy of theoriginal signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between theoriginal and reconstructed signal is small enough to make thereconstructed signal useful for the intended application. In the case ofvideo, lossy compression is widely employed. The amount of distortiontolerated depends on the application; for example, users of certainconsumer streaming applications may tolerate higher distortion thanusers of television contribution applications. The compression ratioachievable can reflect that: higher allowable/tolerable distortion canyield higher compression ratios.

Motion compensation can be a lossy compression technique and can relateto techniques where a block of sample data from a previouslyreconstructed picture or part thereof (reference picture), after beingspatially shifted in a direction indicated by a motion vector (MVhenceforth), is used for the prediction of a newly reconstructed pictureor picture part. In some cases, the reference picture can be the same asthe picture currently under reconstruction. MVs can have two dimensionsX and Y, or three dimensions, the third being an indication of thereference picture in use (the latter, indirectly, can be a timedimension).

In some video compression techniques, an MV applicable to a certain areaof sample data can be predicted from other MVs, for example from thoserelated to another area of sample data spatially adjacent to the areaunder reconstruction, and preceding that MV in decoding order. Doing socan substantially reduce the amount of data required for coding the MV,thereby removing redundancy and increasing compression. MV predictioncan work effectively, for example, because when coding an input videosignal derived from a camera (known as natural video) there is astatistical likelihood that areas larger than the area to which a singleMV is applicable move in a similar direction and, therefore, can in somecases be predicted using a similar motion vector derived fromneighboring area's MVs. That results in the MV found for a given area tobe similar or the same as the MV predicted from the surrounding MVs, andthat in turn can be represented, after entropy coding, in a smallernumber of bits than what would be used if coding the MV directly. Insome cases, MV prediction can be an example of lossless compression of asignal (namely: the MVs) derived from the original signal (namely: thesample stream). In other cases, MV prediction itself can be lossy, forexample because of rounding errors when calculating a predictor fromseveral surrounding MVs.

Various MV prediction mechanisms are described in H.265/HEVC (ITU-T Rec.H.265, “High Efficiency Video Coding”, December 2016). Out of the manyMV prediction mechanisms that H.265 offers, described here is atechnique henceforth referred to as “spatial merge”.

A block may be partitioned into smaller units for processing of theblock. Current signaling trees for a block partition include partitiontypes such as quad tree (QT), binary tree (BT), and ternary tree (TT).However, these partition types may limit coding performance.Accordingly, the inability to accommodate other partition types issignificantly disadvantageous.

SUMMARY

According to an exemplary embodiment, a method of video decoding for adecoder includes acquiring a current picture from a coded videobitstream. The method further includes retrieving signaling informationfrom the coded video bitstream for a block in the current picture. Themethod further includes determining, from the signaling information,whether the block is partitioned in accordance with a quad splitpartition type. The method further includes in response to determiningthat the block is not partitioned in accordance with the quad splitpartition type, determining whether the block is partitioned inaccordance with a split partition type. The method further includes inresponse to determining that the block is partitioned in accordance withthe split partition type, determining whether the block is partitionedin accordance with a non-uniform quad split partition type in which theblock is partitioned into four sub-blocks along a same direction. Themethod further includes in response to determining that the block ispartitioned in accordance with the non-uniform quad split partitiontype, reconstructing the block in accordance with the non-uniform quadsplit partition type.

According to an exemplary embodiment, a video decoder for videodecoding, includes processing circuitry configured to acquire a currentpicture from a coded video bitstream. The processing circuitry isfurther configured to retrieve signaling information from the codedvideo bitstream for a block in the current picture. The processingcircuitry is further configured to determine, from the signalinginformation, whether the block is partitioned in accordance with a quadsplit partition type. The processing circuitry is further configured to,in response to the determination that the block is not partitioned inaccordance with the quad split partition type, determine whether theblock is partitioned in accordance with a split partition type. Theprocessing circuitry is further configured to, in response to thedetermination that the block is partitioned in accordance with the splitpartition type, determine whether the block is partitioned in accordancewith a non-uniform quad split partition type in which the block ispartitioned into four sub-blocks along a same direction, and in responseto the determination that the block is partitioned in accordance withthe non-uniform quad split partition type, reconstruct the block inaccordance with the non-uniform quad split partition type.

According to an exemplary embodiment, a non-transitory computer readablemedium having instructions stored therein, which when executed by aprocessor in a decoder causes the decoder to execute a method thatincludes acquiring a current picture from a coded video bitstream. Themethod further includes retrieving signaling information from the codedvideo bitstream for a block in the current picture. The method furtherincludes determining, from the signaling information, whether the blockis partitioned in accordance with a quad split partition type. Themethod further includes, in response to determining that the block isnot partitioned in accordance with the quad split partition type,determining whether the block is partitioned in accordance with a splitpartition type. The method further includes, in response to determiningthat the block is partitioned in accordance with the split partitiontype, determining whether the block is partitioned in accordance with anon-uniform quad split partition type in which the block is partitionedinto four sub-blocks along a same direction. The method furtherincludes, in response to determining that the block is partitioned inaccordance with the non-uniform quad split partition type,reconstructing the block in accordance with the non-uniform quad splitpartition type.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1 is a schematic illustration of a simplified block diagram of acommunication system (100) in accordance with an embodiment.

FIG. 2 is a schematic illustration of a simplified block diagram of acommunication system (200) in accordance with an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 5 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 6 shows a block diagram of a decoder in accordance with anotherembodiment.

FIGS. 7A and 7B illustrate a quad tree binary tree (QTBT) structure.

FIGS. 8A and 8B illustrate a ternary tree structure.

FIGS. 9A-9J illustrate partition types for block sizes that representinteger powers of 2.

FIGS. 10A-10L illustrate partition types for block sizes that do notrepresent integer powers of 2.

FIG. 11 illustrates an embodiment of a signaling tree.

FIGS. 12A-12H illustrate example partition types.

FIGS. 13A-13B illustrate an embodiment of a non-uniform quad splitpartition type.

FIG. 14 illustrates an embodiment of a signaling tree.

FIG. 15 illustrates an embodiment of a signaling tree.

FIG. 16 illustrates an embodiment of a process performed by a decoder.

FIG. 17 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 illustrates a simplified block diagram of a communication system(100) according to an embodiment of the present disclosure. Thecommunication system (100) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (150). Forexample, the communication system (100) includes a first pair ofterminal devices (110) and (120) interconnected via the network (150).In the FIG. 1 example, the first pair of terminal devices (110) and(120) performs unidirectional transmission of data. For example, theterminal device (110) may code video data (e.g., a stream of videopictures that are captured by the terminal device (110)) fortransmission to the other terminal device (120) via the network (150).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (120) may receive the codedvideo data from the network (150), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (100) includes a secondpair of terminal devices (130) and (140) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (130) and (140)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (130) and (140) via the network (150). Eachterminal device of the terminal devices (130) and (140) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (130) and (140), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 1 example, the terminal devices (110), (120), (130) and(140) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (150) represents any number ofnetworks that convey coded video data among the terminal devices (110),(120), (130) and (140), including for example wireline (wired) and/orwireless communication networks. The communication network (150) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(150) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 2 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (213), that caninclude a video source (201), for example a digital camera, creating forexample a stream of video pictures (202) that are uncompressed. In anexample, the stream of video pictures (202) includes samples that aretaken by the digital camera. The stream of video pictures (202),depicted as a bold line to emphasize a high data volume when compared toencoded video data (204) (or coded video bitstreams), can be processedby an electronic device (220) that includes a video encoder (203)coupled to the video source (201). The video encoder (203) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (204) (or encoded video bitstream (204)),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (202), can be stored on a streamingserver (205) for future use. One or more streaming client subsystems,such as client subsystems (206) and (208) in FIG. 2 can access thestreaming server (205) to retrieve copies (207) and (209) of the encodedvideo data (204). A client subsystem (206) can include a video decoder(210), for example, in an electronic device (230). The video decoder(210) decodes the incoming copy (207) of the encoded video data andcreates an outgoing stream of video pictures (211) that can be renderedon a display (212) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (204),(207), and (209) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Codingor VVC. The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (220) and (230) can includeother components (not shown). For example, the electronic device (220)can include a video decoder (not shown) and the electronic device (230)can include a video encoder (not shown) as well.

FIG. 3 shows a block diagram of a video decoder (310) according to anembodiment of the present disclosure. The video decoder (310) can beincluded in an electronic device (330). The electronic device (330) caninclude a receiver (331) (e.g., receiving circuitry). The video decoder(310) can be used in the place of the video decoder (210) in the FIG. 2example.

The receiver (331) may receive one or more coded video sequences to bedecoded by the video decoder (310); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (301), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (331) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (331) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (315) may be coupled inbetween the receiver (331) and an entropy decoder/parser (320) (“parser(320)” henceforth). In certain applications, the buffer memory (315) ispart of the video decoder (310). In others, it can be outside of thevideo decoder (310) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (310), forexample to combat network jitter, and in addition another buffer memory(315) inside the video decoder (310), for example to handle playouttiming. When the receiver (331) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (315) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (315) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (310).

The video decoder (310) may include the parser (320) to reconstructsymbols (321) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (310),and potentially information to control a rendering device such as arender device (312) (e.g., a display screen) that is not an integralpart of the electronic device (330) but can be coupled to the electronicdevice (330), as was shown in FIG. 3. The control information for therendering device(s) may be in the form of Supplementary EnhancementInformation (SEI messages) or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (320) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (320) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (320) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (320) may perform entropy decoding/parsing operation on thevideo sequence received from the buffer memory (315), so as to createsymbols (321).

Reconstruction of the symbols (321) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (320). The flow of such subgroup control information between theparser (320) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (310)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (351). Thescaler/inverse transform unit (351) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (321) from the parser (320). The scaler/inversetransform unit (351) can output blocks comprising sample values, thatcan be input into aggregator (355).

In some cases, the output samples of the scaler/inverse transform (351)can pertain to an intra coded block; that is: a block that is not usingpredictive information from previously reconstructed pictures, but canuse predictive information from previously reconstructed parts of thecurrent picture. Such predictive information can be provided by an intrapicture prediction unit (352). In some cases, the intra pictureprediction unit (352) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (358). The currentpicture buffer (358) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(355), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (352) has generated to the outputsample information as provided by the scaler/inverse transform unit(351).

In other cases, the output samples of the scaler/inverse transform unit(351) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (353) canaccess reference picture memory (357) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (321) pertaining to the block, these samples can beadded by the aggregator (355) to the output of the scaler/inversetransform unit (351) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (357) from where themotion compensation prediction unit (353) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (353) in the form of symbols (321) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (357) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (355) can be subject to variousloop filtering techniques in the loop filter unit (356). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (356) as symbols (321) from the parser (320), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (356) can be a sample stream that canbe output to the render device (312) as well as stored in the referencepicture memory (357) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (320)), the current picture buffer (358) can becomea part of the reference picture memory (357), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (310) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as document in thevideo compression technology or standard. Specifically, a profile canselect a certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (331) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (310) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 4 shows a block diagram of a video encoder (403) according to anembodiment of the present disclosure. The video encoder (403) isincluded in an electronic device (420). The electronic device (420)includes a transmitter (440) (e.g., transmitting circuitry). The videoencoder (403) can be used in the place of the video encoder (203) in theFIG. 2 example.

The video encoder (403) may receive video samples from a video source(401)(that is not part of the electronic device (420) in the FIG. 4example) that may capture video image(s) to be coded by the videoencoder (403). In another example, the video source (401) is a part ofthe electronic device (420).

The video source (401) may provide the source video sequence to be codedby the video encoder (403) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . )and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (401) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (401) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focusses on samples.

According to an embodiment, the video encoder (403) may code andcompress the pictures of the source video sequence into a coded videosequence (443) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (450). In some embodiments, the controller(450) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (450) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (450) can be configured to have other suitablefunctions that pertain to the video encoder (403) optimized for acertain system design.

In some embodiments, the video encoder (403) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (430) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (433)embedded in the video encoder (403). The decoder (433) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (434). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (434) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (433) can be the same as of a“remote” decoder, such as the video decoder (310), which has alreadybeen described in detail above in conjunction with FIG. 3. Brieflyreferring also to FIG. 3, however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (445) and the parser (320) can be lossless, the entropy decodingparts of the video decoder (310), including the buffer memory (315), andparser (320) may not be fully implemented in the local decoder (433).

An observation that can be made at this point is that any decodertechnology except the parsing/entropy decoding that is present in adecoder also necessarily needs to be present, in substantially identicalfunctional form, in a corresponding encoder. For this reason, thedisclosed subject matter focuses on decoder operation. The descriptionof encoder technologies can be abbreviated as they are the inverse ofthe comprehensively described decoder technologies. Only in certainareas a more detail description is required and provided below.

During operation, in some examples, the source coder (430) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously-coded picture fromthe video sequence that were designated as “reference pictures”. In thismanner, the coding engine (432) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (433) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (430). Operations of the coding engine (432) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 4), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (433) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture cache (434). In this manner, the video encoder(403) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (435) may perform prediction searches for the codingengine (432). That is, for a new picture to be coded, the predictor(435) may search the reference picture memory (434) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(435) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (435), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (434).

The controller (450) may manage coding operations of the source coder(430), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (445). The entropy coder (445)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies known to a person skilled in the art as, for exampleHuffman coding, variable length coding, arithmetic coding, and so forth.

The transmitter (440) may buffer the coded video sequence(s) as createdby the entropy coder (445) to prepare for transmission via acommunication channel (460), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(440) may merge coded video data from the video coder (403) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (450) may manage operation of the video encoder (403).During coding, the controller (450) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of Intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A Predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A Bi-directionally Predictive Picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of 1 pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference pictures. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (403) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (403) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (440) may transmit additional datawith the encoded video. The source coder (430) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, Supplementary EnhancementInformation (SEI) messages, Visual Usability Information (VUI) parameterset fragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to Intra prediction) makes uses of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first and a second reference picture thatare both prior in decoding order to the current picture in the video(but may be in the past and future, respectively, in display order) areused. A block in the current picture can be coded by a first motionvector that points to a first reference block in the first referencepicture, and a second motion vector that points to a second referenceblock in the second reference picture. The block can be predicted by acombination of the first reference block and the second reference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTUs) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quad tree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels and the like.

FIG. 5 shows a diagram of a video encoder (503) according to anotherembodiment of the disclosure. The video encoder (503) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (503) is used in theplace of the video encoder (203) in the FIG. 2 example.

In an HEVC example, the video encoder (503) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (503) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (503) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(503) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (503) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 5 example, the video encoder (503) includes the interencoder (530), an intra encoder (522), a residue calculator (523), aswitch (526), a residue encoder (524), a general controller (521) and anentropy encoder (525) coupled together as shown in FIG. 5.

The inter encoder (530) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique.

The intra encoder (522) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform and, in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques).

The general controller (521) is configured to determine general controldata and control other components of the video encoder (503) based onthe general control data. In an example, the general controller (521)determines the mode of the block, and provides a control signal to theswitch (526) based on the mode. For example, when the mode is the intra,the general controller (521) controls the switch (526) to select theintra mode result for use by the residue calculator (523), and controlsthe entropy encoder (525) to select the intra prediction information andinclude the intra prediction information in the bitstream; and when themode is the inter mode, the general controller (521) controls the switch(526) to select the inter prediction result for use by the residuecalculator (523), and controls the entropy encoder (525) to select theinter prediction information and include the inter predictioninformation in the bitstream.

The residue calculator (523) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (522) or the inter encoder (530). Theresidue encoder (524) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (524) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients.

The entropy encoder (525) is configured to format the bitstream toinclude the encoded block. The entropy encoder (525) is configured toinclude various information according to a suitable standard, such asHEVC standard. In an example, the entropy encoder (525) is configured toinclude the general control data, the selected prediction information(e.g., intra prediction information or inter prediction information),the residue information, and other suitable information in thebitstream. Note that, according to the disclosed subject matter, whencoding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 6 shows a diagram of a video decoder (610) according to anotherembodiment of the disclosure. The video decoder (610) is configured toreceive a coded pictures that are part of a coded video sequence, anddecode the coded picture to generate a reconstructed picture. In anexample, the video decoder (610) is used in the place of the videodecoder (210) in the FIG. 2 example.

In the FIG. 6 example, the video decoder (610) includes an entropydecoder (671), an inter decoder (680), a residue decoder (673), areconstruction module (674), and an intra decoder (672) coupled togetheras shown in FIG. 6.

The entropy decoder (671) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example,intra, inter, b-predicted, the latter two in merge submode or anothersubmode), prediction information (such as, for example, intra predictioninformation or inter prediction information) that can identify certainsample or metadata that is used for prediction by the intra decoder(672) or the inter decoder (680) respectively residual information inthe form of, for example, quantized transform coefficients, and thelike. In an example, when the prediction mode is inter or bi-predictedmode, the inter prediction information is provided to the inter decoder(680); and when the prediction type is the intra prediction type, theintra prediction information is provided to the intra decoder (672). Theresidual information can be subject to inverse quantization and isprovided to the residue decoder (673).

The inter decoder (680) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (672) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (673) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (673) mayalso require certain control information (to include the QuantizerParameter QP), and that information may be provided by the entropydecoder (671) (datapath not depicted as this may be low volume controlinformation only).

The reconstruction module (674) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (673) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (203), (403) and (503), and thevideo decoders (210), (310) and (610) can be implemented using anysuitable technique. In an embodiment, the video encoders (203), (403)and (503), and the video decoders (210), (310) and (610) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (203), (403) and (403), and the videodecoders (210), (310) and (610) can be implemented using one or moreprocessors that execute software instructions.

According to some embodiments, a CTU is split into CUs by using a quadtree binary tree (QTBT) structure denoted as a coding tree to adapt tovarious local characteristics of individual blocks included in the CUs.The decision whether to code a picture area using inter-picture(temporal) or intra-picture (spatial) prediction may be performed at theCU level. Each CU may be further split into one, two or four PUsaccording to a PU splitting type. In some embodiments, inside one PU,the same prediction process is applied and the relevant information istransmitted to the decoder on a PU basis. After obtaining the residualblock by applying the prediction process based on the PU splitting type,a CU may be partitioned into TUs according to another quad treestructure similar to the quad tree structure used for the coding treefor the CTU. In some other embodiments, a PU contains only one TU thathas the same shape as the PU.

The coding tree for the CTU may include multiple partition typesincluding CU, PU, and TU. In some embodiments, a CU or a TU is only asquare shape, while a PU may be square or rectangular shape for an interpredicted block. In other embodiments, rectangular shaped CUs, PUs, andTUs are permitted. At a picture boundary, an implicit quad tree splitmay be applied so that a block will keep quad tree splitting until thesize of the split block fits the picture boundary. According to someembodiments, an implicit split means that a split flag is not signaledbut implied instead. For example, implicit QT means only a QT split isallowed for a pictureboundary block. As such, the split flag is notsignaled at the picture boundary. As an another example, when only a BTsplit is allowed at the picture boundary, the implicit split is thebinary split. In some embodiments, when both QT and BT are allowed atthe picture boundary, there is no implicit split, and the split methodis explicitly signaled.

According to some embodiments, the QTBT structure does not includemultiple partition types (e.g., QTBT does not include the separation ofthe CU, PU and TU), and supports more flexibility for CU partitionshapes. For example, in the QTBT block structure, a CU may have either asquare or rectangular shape. FIG. 7A illustrates an example CTU (700)that is partitioned by the QTBT structure. For example, the CTU (700) ispartitioned into four equal sized sub-CUs (A), (B), (C), and (D). FIG.7B illustrates a corresponding coding tree that illustrates branchescorresponding to sub-CUs (A), (B), (C), and (D). The solid linesindicate quad tree splitting, and the dotted lines indicate binary treesplitting. The binary tree structure may include two splitting types:(i) symmetric horizontal splitting and (ii) symmetric verticalsplitting. In each splitting (i.e., non-leaf) node of the binary tree,one flag may be signalled to indicate which splitting type (e.g.,horizontal or vertical) is used, where 0 indicates horizontal splittingand 1 indicates vertical splitting or vice versa. For the quad treesplitting, the splitting type is not indicated since quad tree splittingsplits a block both horizontally and vertically to produce 4 sub-blockswith an equal size.

As illustrated in FIGS. 7A and 7B, the sub-CU (A) is first partitionedinto two sub-blocks by a vertical split, where the left sub-block ispartitioned again by another vertical split. The sub-CU (B) is furtherpartitioned by a horizontal split. The sub-CU (C) is further partitionedby another quad split partition. The upper left sub-block of sub-CU (C)is partitioned by a vertical split, and subsequently partitioned by ahorizontal split. Furthermore, the lower right sub-block of sub-CU (C)is partitioned by a horizontal split. The upper right and lower leftsub-blocks of sub-CU (C) are not further partitioned. The sub-CU (D) isnot partitioned further and thus, does not include any additional leafnodes in the coding tree below the “D” branch.

The binary tree leaf nodes may be referred to as CUs, where the binarysplitting may be used for prediction and transform processing withoutany further partitioning, which means that the CU, PU, and TU have thesame block size in the QTBT coding block structure. A CU may includecoding blocks (CBs) of different colour components. For example, one CUmay contain one luma CB and two chroma CBs in the case of P and B slicesof a 4:2:0 chroma format, and sometimes contain a CB of a singlecomponent (e.g., one CU contains only one luma CB or just two chroma CBsin the case of Intra-pictures or I slices). In some embodiments, inintra-pictures or I-slices, the TU width or height is constrained to notexceed a given limit (e.g., 64 for luma and 32 for chroma). If the CBwidth or height is larger than the limit, then the TU is further splituntil the TU's size does not exceed the limit.

According to some embodiments, the QTBT partitioning scheme includes thefollowing parameters:

-   -   CTU size: the root node size of a quad tree    -   MinQTSize: the minimum allowed quad tree leaf node size    -   MaxBTSize: the maximum allowed binary tree root node size    -   MaxBTDepth: the maximum allowed binary tree depth    -   MinBTSize: the minimum allowed binary tree leaf node size

In one example of the QTBT partitioning structure, the CTU size is setas 128×128 luma samples with two corresponding 64×64 blocks of chromasamples, the MinQTSize is set as 16×16, the MaxBTSize is set as 64×64,the MinBTSize (for both width and height) is set as 4×4, and theMaxBTDepth is set as 4. The QTBT partitioning structure is applied tothe CTU first to generate quad tree leaf nodes. The quad tree leaf nodesmay have a size from 16×16 (i.e., the MinQTSize) to 128×128 (i.e., theCTU size). If the leaf quad tree node is 128×128, the leaf quad treenode will not be further split by the binary tree since the size exceedsthe MaxBTSize (i.e., 64×64). Otherwise, the leaf quad tree node may befurther partitioned by the binary tree. Therefore, the quad tree leafnode is also the root node for the binary tree and the quad tree leafhas the binary tree depth as 0. When the binary tree depth reaches theMaxBTDepth (e.g., 4), no further splitting is performed. When the binarytree node has width equal to the MinBTSize (e.g., 4), no furtherhorizontal splitting is performed. Similarly, when the binary tree nodehas a height equal to MinBTSize, no further vertical splitting isperformed. The leaf nodes of the binary tree are further processed byprediction and transform processing without any further partitioning. Insome embodiments, the maximum CTU size is 256×256 luma samples.

The QTBT partition structure may further support the ability for theluma and chroma components to each have separate QTBT structures. Forexample, for P and B slices, the luma and chroma CTBs in one CTU mayshare the same QTBT structure. However, for I slices, the luma CTB ispartitioned into CUs by a QTBT structure, and the chroma CTBs arepartitioned into chroma CUs by another QTBT structure. Therefore, inthis example, a CU in an I slice contains a coding block of the lumacomponent or coding blocks of two chroma components, and a CU in a P orB slice contains coding blocks of all three colour components.

In some embodiments, inter prediction for small blocks is restricted toreduce the memory access requirements of motion compensation, such thatbi-prediction is not supported for 4×8 and 8×4 blocks, and interprediction is not supported for 4×4 blocks. In other embodiments, theQTBT partition scheme does not include these restrictions.

According to some embodiments, a Multi-type-tree (MTT) structureincludes (i) quad tree splitting, (ii) binary tree splitting, and (iii)horizontal and vertical center-side ternary trees. FIG. 8A illustratesan embodiment of a vertical center-side ternary tree and FIG. 8Billustrates an example of a horizontal center-side ternary tree.Compared to the QTBT structure, MTT can be a more flexible treestructure since additional structures are permitted.

Ternary tree partitioning includes significantly advantageous featuressuch as providing a complement to quad tree and binary tree partitioningwhere ternary tree partitioning is able to capture objects which arelocated in a block center, whereas quad tree and binary tree split alongthe block center. As another advantage of ternary tree partitioning, thewidth and height of the partitions of the proposed ternary trees are apower of 2 so that no additional transforms are needed. A two-level treeprovides the advantage of complexity reduction. As an example, thecomplexity of traversing a tree is T^(D), where T denotes the number ofsplit types, and D is the depth of tree.

According to some embodiments, binary splitting includes shifting of thesplit. In this regard, the split of a block is performed away from thecenter of the block such that at least two resulting sub-blocksresulting from the split are not the same size. For example, each blockis either not split or is split into two rectangular blocks either inthe horizontal or the vertical direction. In some embodiments, both thewidth and height in the luma samples of the resulting CUs representinteger multiples of 4. As an example, dim represents the width (forvertical splits) or the height (for horizontal splits), in luma samples,of the block to be split. Referring to FIGS. 9A-9J and FIGS. 10A-10L,for both split directions, the following splits may be supported:

-   -   (i) ½ split (FIGS. 9A and 9B): This split is supported if        dim≥k·8, k∈        .    -   (ii) ¼ split and ¾ split (FIGS. 9C-9F): These splits are        supported if dim represents an integer power of two (dim=2^(n),        n∈        ) and dim≥16.    -   (iii) ⅜ split and ⅝ split (FIGS. 9G-9J): These splits are        supported if dim represents an integer power of two (dim=2^(n),        n∈        ) and dim≥32.    -   (iv) ⅓ split and ⅔ split (FIGS. 10A-10D): These splits are        supported if dim=3·2^(n), n∈        and dim≥12.    -   (v) ⅕ split, ⅖ split, ⅗ split and ⅘ split (FIGS. 10E-10L): These        splits are supported if dim=5·2^(n), n∈        and dim≥20.

In some embodiments, an n/m horizontal split specifies a split in whichthe ratio of the height of the first resulting block (i.e., top block)and the height of the block to be split is equal to n/m. Furthermore, insome embodiments, an n/m vertical split specifies a split in which theratio of the width of the first resulting block (i.e., left block) andthe width of the block to be split is equal to n/m. If the size of theside to be split is not equal to 2^(n), n∈

, then the size of the side to be split is either equal to 3·2^(n), n∈

or 5·2^(n), n∈

.

According to some embodiments, a binary split is uniquely determined bya split direction and split ratio. The direction of the binary splitsmay be coded depending on the previous split. In this regard, instead ofbeing signaled as a horizontal or a vertical split, the direction of thebinary split may be signaled as a perpendicular split or a parallelsplit which, may be translated to a horizontal or vertical split. Insome embodiments, at the root level, when no previous split is signaled,the first perpendicular split is a horizontal split and the firstparallel split is a vertical split. A binary flag (e.g.,perpend_split_flag) may distinguish between the two possible directions(i.e., perpendicular and parallel). The split ratio may describe thelocation where to split as illustrated in FIGS. 9A-9J and FIGS. 10A-10L.The type of split for a block may be coded using a binary decision tree.FIG. 11 illustrates an example signaling tree (1100) for a quad treewith binary splits with shifting (QT+BTS) without any restrictions. Asillustrated in FIG. 11, both the split direction as well as the splitratio are coded using context-based adaptive arithmetic coding (CABAC).As an example, the counting of the binary tree depth starts with thefirst split that is not a perpendicular ½ split. The portion of the treeunder the “perpendicular” node is not shown since it is the same as theportion of the tree under the “parallel” node.

According to some embodiments, a signaling tree may include anasymmetric binary tree (ABT) block partitioning structure. FIGS. 12A-12Hillustrate various split partition types. For example, FIG. 12Aillustrates a no-split partition type. FIG. 12B illustrates a quad splitpartition type, where a block is split into four equal sub-blocks alongthe horizontal and vertical directions. FIGS. 12C and 12D illustratehorizontal and vertical binary split partition types, respectively,where a block is split into two equal sub-blocks along a respectivedirection. As shown in FIGS. 12E-12H, a block can be partitioned using1:3 or 3:1 partitions such as HOR_UP (FIG. 12E), HOR_DOWN (FIG. 12F),VER_LEFT (FIG. 12G), and VER_RIGHT (FIG. 12H). For both BTS and ABT, thewidth or height of a partition may be a non-power-of-2. In someembodiments, a restricted BTS is tested, where a non-power-of-2partition is allowed, but a non-power-of-2 partition is further split sothat the final coding unit has both a width and a height that is a powerof 2.

According to some embodiments, at a picture boundary, when a partitionof a CTU results in areas that are both inside and outside of thepicture boundary, the CTU is further partitioned into smaller codingunits. In one embodiment, a CTU at a picture boundary is splitrecursively using an implicit quad tree, as discussed above. In thisembodiment, a split flag is implied and not signaled. In anotherembodiment, a set of partitions combined with a QT split at the pictureboundary is tested, including QT+BT, QT+BT+TT, QT+BT+ABT, QT+BTS. Ateach split level, when both QT and non-QT splits are both available atthe picture boundary, one or more flags may be signaled to indicatewhich split is applied.

According to some embodiments, a non-uniform quad-split partition typeincludes splitting a block into four sub-blocks along a same direction.A non-uniform quad-split may be performed on a CU, PU, or TU. The ratioof the sub-blocks after the non-uniform quad split is performed may be1:4:1:2. The non-uniform quad split may be applied along either thehorizontal or vertical direction. FIGS. 13A and 13B illustrate examplesof a non-uniform quad split partition type with a vertical ratio of1:2:4:1 and a horizontal ratio of 1:4:1:2, respectively

According to some embodiments, when applying the non-uniform quad splitpartition type, the four sub-blocks may have the relative area ratio of1, 1, 2, 4. There are a total of 12 possible combinations of the ratio:(i) 1:1:2:4, (ii) 1:1:4:2, (iii) 1:2:1:4, (iv) 1:2:4:1, (v) 1:4:1:2,(vi) 1:4:2:1, (vii) 2:1:1:4, (viii) 2:1:4:1, (ix) 2:4:1:1, (x) 4:1:1:2,(xi) 4:1:2:1, and (xii) 4:2:1:1. As an example, when applying ahorizontal non-uniform quad split with a ratio of 1:2:4:1 on a 64×64block, the sub-blocks have sizes of 64×8, 64×16, 64×32, and 64×8.

In one embodiment, all the 12 ratio combinations are allowed. Eachcombination may be represented by an index from 0 to 11. In otherembodiments, restrictions are applied on the possible combination ofratios. In one embodiment, only 8 ratio combinations are permitted(e.g., 1:2:1:4, 1:2:4:1, 1:4:1:2, 1:4:2:1, 2:1:1:4, 2:1:4:1, 4:1:1:2,4:1:2:1). Each of these restricted combinations may be represented by anindex from 0 to 7. In another embodiment, only 4 ratio combinations arepermitted (e.g., 1:2:4:1, 1:4:1:2, 1:4:2:1, 2:1:4:1). Each of theserestricted combinations may be represented by an index from 0 to 3. Inanother embodiment, the permitted non-uniform quad split ratios may bearranged in any arbitrary order.

In some embodiments, the index number indicating which ratio is beingapplied is binarized using truncated unary coding. In anotherembodiment, the index number indicating which ratio is being applied isbinarized using fixed length coding. In another embodiment, the indexnumber indicating which ratio is being applied is binarized withtruncated unary plus fixed length coding.

According to some embodiments, when a non-QT split partition type isindicated, a binary value is conditionally signaled on top of theQT+BT-FTemary Tree (TT) structure to indicate whether the non-uniformquad split partition type is applied. In some embodiments, the binaryvalue is a binary symbol that is to be compressed by the entropy encoder(525). The entropy encoder (525) may only take binary inputs, and thus,a non-binary symbol goes through a process called “binarization” to beconverted to a series of bins (i.e., codeword, binary values). In oneembodiment, after the horizontal/vertical direction has been indicatedin signaling information that includes a signaling tree, a bin in thesignaling tree indicates whether the partition type is BT or non-BT.When the bin indicates that the split partition type is non-BT, anotherbin may further indicate whether the partition type is TT or non-uniformquad split partition type. FIG. 14 illustrates an embodiment of asignaling tree (1400) without restriction (i.e., flags indicating arestriction type are signaled instead of inferred). The set of codewordsfor the tree (1400) may be in accordance with the following Table I if 8of the 12 possible non-uniform quad split partition type combinationsare used. The 8 combinations of the non-uniform quad split partitiontypes may be binarized with fixed length coding.

TABLE I Partition Type Codeword Quad split (split to four same-sizesub-blocks, 1 all with half width and half height of the parent block)Non-split 00 Horizontal binary split 0100 Horizontal ternary split 01010Horizontal non-uniform quad split 1:2:1:4 01011000 Horizontalnon-uniform quad split 1:2:4:1 01011001 Horizontal non-uniform quadsplit 1:4:1:2 01011010 Horizontal non-uniform quad split 1:4:2:101011011 Horizontal non-uniform quad split 2:1:1:4 01011100 Horizontalnon-uniform quad split 2:1:4:1 01011101 Horizontal non-uniform quadsplit 4:1:1:2 01011110 Horizontal non-uniform quad split 4:1:2:101011111 Vertical binary split 0110 Vertical ternary split 01110Vertical non-uniform quad split 1:2:1:4 01111000 Vertical non-uniformquad split 1:2:4:1 01111001 Vertical non-uniform quad split 1:4:1:201111010 Vertical non-uniform quad split 1:4:2:1 01111011 Verticalnon-uniform quad split 2:1:1:4 01111100 Vertical non-uniform quad split2:1:4:1 01111101 Vertical non-uniform quad split 4:1:1:2 01111110Vertical non-uniform quad split 4:1:2:1 01111111

As illustrated in Table I, each codeword uniquely identifies aparticular partition type. For example, if a block has a codeword01011000, then the block is partitioned in accordance with a horizontalnon-uniform quad split partition type with the 4 sub-blocks having aratio of 1:2:1:4. Table II illustrates another example set of codewordsfor the tree (1400) if 4 of the 12 possible combinations of non-uniformquad split partition types are used. The 4 combinations of thenon-uniform quad split partition types may be binarized with fixedlength coding.

TABLE II Quad split (split to four same-size sub-blocks, 1 all with halfwidth and half height) Non-split 00 Horizontal binary split 0100Horizontal ternary split 01010 Horizontal non-uniform quad split 1:2:4:10101100 Horizontal non-uniform quad split 1:4:1:2 0101101 Horizontalnon-uniform quad split 1:4:2:1 0101110 Horizontal non-uniform quad split2:1:4:1 0101111 Vertical binary split 0110 Vertical ternary split 01110Vertical non-uniform quad split 1:2:4:1 0111100 Vertical non-uniformquad split 1:4:1:2 0111101 Vertical non-uniform quad split 1:4:2:10111110 Vertical non-uniform quad split 2:1:4:1 0111111

According to some embodiments, the signaling tree (1400) is included assignaling information in a coded video bitstream. Determining apartition type of a block using the signaling tree (1400) may beperformed as follows. The root of the signaling tree is the Start node,where it is determined if a block is split in accordance with the quadtree split partition type (FIG. 12B) (e.g., “QT” node). If the block isnot split in accordance with the quad tree split partition type, then atthe “Non-QT” node, it is determined whether the block is split. If theblock is not split, then the process ends at the “No Split” node, wherethere is no partition of the block (FIG. 12A). However, if the block issplit, then at the “Split” node, it is determined whether the block issplit in either the horizontal direction (i.e., “Horizontal” node) orthe vertical direction (i.e., “Vertical” node). The leafs of the treeunder the “Vertical” node are not displayed since these leafs areidentical to the leafs under the “Horizontal” node. At the “Horizontal”node, it is determined whether the block is split in accordance with abinary tree split partition type (i.e., “BT” node, FIG. 12C), or anon-binary tree split partition type. If the block is split inaccordance with a non-binary tree split partition type, then at the“Non-BT” node, it is determined whether the block is split in accordancewith the ternary tree split partition type (i.e., “TT” node, FIG. 8B) orthe non-uniform quad split partition type (i.e., “Non-Uniform QuadSplit” node, FIG. 13B).

FIG. 15 illustrates another embodiment of a signaling tree (1500). Thetree (1500) is the same as tree (1400) from the root “Start” node to the“Horizontal” and “Vertical” nodes. However, at the “Horizontal” node, itis determined whether the block is split in accordance with thenon-uniform quad split partition type (i.e., “Non-Uniform Quad Split”node, FIG. 13B). If the block is not split in accordance with thenon-uniform quad split partition type, then at the “BT/TT” node, it isdetermined whether the block is partitioned in accordance with thebinary tree split partition type (i.e., “BT” node, FIG. 12C) or theternary tree split partition type (i.e., “TT” node, FIG. 8B).

According to some embodiments, restrictions of the CU shape and/or sizemay apply on the non-uniform quad split. In one embodiment, thenon-uniform quad-split is applied on the block only when the number ofpixels on the edge perpendicular to the split direction is greater thanor equal to a predetermined value (e.g., 32). For example, a 64×8 blockis allowed to be split into four sub-blocks with size of 8×8, 16×8,32×8, and 8×8. In another example, a 16×16 block is not allowed to besplit in accordance with the non-uniform quad split in either thehorizontal or vertical direction.

In another embodiment, when a split of a block in accordance with thenon-uniform quad split results in regions both inside and outside thepicture boundary, the non-uniform quad split is allowed only when one ofthe sub-block boundaries along the split direction is also the pictureboundary. For example, when a 64×8 block is at the picture boundary,with 40×8 inside the picture and 24×8 outside the picture, then the1:2:4:1 split ratio is not allowed, but the 1:4:2:1 split ratio isallowed. When a non-uniform quad split is allowed at the pictureboundary, the split may not be signaled but inferred.

FIG. 16 illustrates an embodiment of a process performed by a decodersuch as video decoder (610). The process may generally start at step(S1600) where a current picture is acquired from a coded videobitstream. The process proceeds to step (S1602) where signalinginformation is retrieved from the coded video bit stream for a block inthe current picture. For example, the signaling information may includeone of the signaling trees included in either FIG. 14 or 15.

The process proceeds to step (S1604) to determine whether the block ispartitioned in accordance with a quad split partition type. If the blockis partitioned in accordance with a quad split partition type, theprocess proceeds to step (S1606) where the block is reconstructed inaccordance with the quad split partition type. FIG. 12B illustrates anexample of a block that is partitioned in accordance with the quad splitpartition type. As illustrated in FIG. 12B, the block is partitionedinto four equal sized sub-blocks.

Returning to step (S1604), if the block is not partitioned in accordancewith the quad split partition type, the process proceeds to step (S1608)to determine whether the block is partitioned in accordance with thesplit partition type. If the block is not partitioned in accordance withthe split partition type, the process proceeds to step (S1610) where theblock is reconstructed in accordance with the non-split partition type.As an example, FIG. 12A illustrates a block that is not partitioned(i.e., non-split partition type).

Returning to step (S1608), if the block is partitioned in accordancewith a split partition type, the process proceeds to step (S1612) todetermine whether the block is partitioned in accordance with anon-uniform quad split partition type. If the block is partitioned inaccordance with the non-uniform quad split partition type, the processproceeds to step (S1614) where the block is reconstructed in accordancewith the non-uniform quad split partition type. FIGS. 13A and 13Billustrate examples of a block partitioned in accordance with thenon-uniform split partition type. If the block is not partitioned inaccordance with the non-uniform quad split partition type, the processproceeds to step (S1616) where the block is reconstructed in accordancewith the binary or ternary split partition type. For example, referringto the signaling trees illustrated in FIGS. 14 and 15, after it isdetermined that a block is split, the block is split in accordance witheither the non-uniform quad split partition type, the binary tree splitpartition type, and the ternary tree split partition type. Thus, if ablock is not split according to the non-uniform quad split partitiontype, then the block is either split in accordance with the binary treesplit partition type or the ternary tree split partition type. FIGS. 12Cand 12D provide examples of the binary split partition type, and FIGS.8A and 8B provide examples of the ternary tree split partition type. Theprocess illustrated in FIG. 16 may be terminated after either one ofsteps (S1606), (S1610), (S1614), or (S1616) are performed.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 17 shows a computersystem (1700) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 17 for computer system (1700) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1700).

Computer system (1700) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1701), mouse (1702), trackpad (1703), touchscreen (1710), data-glove (not shown), joystick (1705), microphone(1706), scanner (1707), camera (1708).

Computer system (1700) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1710), data-glove (not shown), or joystick (1705), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1709), headphones(not depicted)), visual output devices (such as screens (1710) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability—some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1700) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1720) with CD/DVD or the like media (1721), thumb-drive (1722),removable hard drive or solid state drive (1723), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1700) can also include an interface to one or morecommunication networks. Networks can for example be wireless, wireline,optical. Networks can further be local, wide-area, metropolitan,vehicular and industrial, real-time, delay-tolerant, and so on. Examplesof networks include local area networks such as Ethernet, wireless LANs,cellular networks to include GSM, 3G, 4G, 5G, LTE and the like, TVwireline or wireless wide area digital networks to include cable TV,satellite TV, and terrestrial broadcast TV, vehicular and industrial toinclude CANBus, and so forth. Certain networks commonly require externalnetwork interface adapters that attached to certain general purpose dataports or peripheral buses (1749) (such as, for example USB ports of thecomputer system (1700)); others are commonly integrated into the core ofthe computer system (1700) by attachment to a system bus as describedbelow (for example Ethernet interface into a PC computer system orcellular network interface into a smartphone computer system). Using anyof these networks, computer system (1700) can communicate with otherentities. Such communication can be uni-directional, receive only (forexample, broadcast TV), uni-directional send-only (for example CANbus tocertain CANbus devices), or bi-directional, for example to othercomputer systems using local or wide area digital networks. Certainprotocols and protocol stacks can be used on each of those networks andnetwork interfaces as described above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1740) of thecomputer system (1700).

The core (1740) can include one or more Central Processing Units (CPU)(1741), Graphics Processing Units (GPU) (1742), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1743), hardware accelerators for certain tasks (1744), and so forth.These devices, along with Read-only memory (ROM) (1745), Random-accessmemory (1746), internal mass storage such as internal non-useraccessible hard drives, SSDs, and the like (1747), may be connectedthrough a system bus (1748). In some computer systems, the system bus(1748) can be accessible in the form of one or more physical plugs toenable extensions by additional CPUs, GPU, and the like. The peripheraldevices can be attached either directly to the core's system bus (1748),or through a peripheral bus (1749). Architectures for a peripheral businclude PCI, USB, and the like.

CPUs (1741), GPUs (1742), FPGAs (1743), and accelerators (1744) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1745) or RAM (1746). Transitional data may be also stored in RAM(1746), whereas permanent data can be stored for example, in theinternal mass storage (1747). Fast storage and retrieve to any of thememory devices can be enabled through the use of cache memory, that canbe closely associated with one or more CPU (1741), GPU (1742), massstorage (1747), ROM (1745), RAM (1746), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1700), and specifically the core (1740) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1740) that are of non-transitorynature, such as core-internal mass storage (1747) or ROM (1745). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1740). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1740) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1746) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1744)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

APPENDIX A: ACRONYMS

MV: Motion Vector

HEVC: High Efficiency Video Coding

SEI: Supplementary Enhancement Information

VUI: Video Usability Information

GOPs: Groups of Pictures

TUs: Transform Units,

PUs: Prediction Units

CTUs: Coding Tree Units

CTBs: Coding Tree Blocks

PBs: Prediction Blocks

HRD: Hypothetical Reference Decoder

SNR: Signal Noise Ratio

CPUs: Central Processing Units

GPUs: Graphics Processing Units

CRT: Cathode Ray Tube

LCD: Liquid-Crystal Display

OLED: Organic Light-Emitting Diode

CD: Compact Disc

DVD: Digital Video Disc

ROM: Read-Only Memory

RAM: Random Access Memory

ASIC: Application-Specific Integrated Circuit

PLD: Programmable Logic Device

LAN: Local Area Network

GSM: Global System for Mobile communications

LTE: Long-Term Evolution

CANBus: Controller Area Network Bus

USB: Universal Serial Bus

PCI: Peripheral Component Interconnect

FPGA: Field Programmable Gate Areas

SSD: solid-state drive

IC: Integrated Circuit

CU: Coding Unit

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

(1) A method of video decoding for a decoder, the method includingacquiring a current picture from a coded video bitstream; retrievingsignaling information from the coded video bitstream for a block in thecurrent picture; determining, from the signaling information, whetherthe block is partitioned in accordance with a quad split partition type;in response to determining that the block is not partitioned inaccordance with the quad split partition type, determining whether theblock is partitioned in accordance with a split partition type; inresponse to determining that the block is partitioned in accordance withthe split partition type, determining whether the block is partitionedin accordance with a non-uniform quad split partition type in which theblock is partitioned into four sub-blocks along a same direction; and inresponse to determining that the block is partitioned in accordance withthe non-uniform quad split partition type, reconstructing the block inaccordance with the non-uniform quad split partition type.

(2) The method of according to feature (1), in which the determiningwhether the block is partitioned in accordance with the non-uniform quadsplit partition type further includes: determining whether the block ispartitioned in accordance with one of (i) a binary split partition typein which the block is partitioned into two sub-blocks along a samedirection and (ii) a non-binary split partition type, and in response todetermining that the block is partitioned in accordance with thenon-binary split partition type, determining whether the block ispartitioned in accordance with one of (i) a ternary split partition typein which the block is partitioned into three sub-blocks along a samedirection and (ii) the non-uniform quad split partition type.

(3) The method according to feature (1) or (2), in which the determiningwhether the block is partitioned in accordance with the non-uniform quadsplit further includes: determining whether the block is partitioned inaccordance with one of (i) a non-quad split partition type, and (ii) thenon-uniform quad split partition type.

(4) The method of according to feature (3), in which in response todetermining that the block is partitioned in accordance with thenon-quad partition type, determining whether the block is partitioned inaccordance with one of (i) a binary split partition type in which theblock is partitioned into two sub-blocks along a same direction and (ii)a ternary split partition type in which the block is partitioned intothree sub-blocks along a same direction.

(5) The method of according to feature (1), in which the blockpartitioned in accordance with the non-uniform quad partition split typeincludes first and second sub-blocks of a same fixed size, a thirdsub-block that is twice the fixed size, and fourth sub-block that isfour times the fixed size.

(6) The method according to feature (5), in which the first and secondsub-blocks are adjacent to each other.

(7) The method according to feature (5), in which the first and secondblocks are not adjacent to each other.

(8) The method according to feature (5), in which the first sub-block isbetween the third sub-block and the fourth sub-block.

(9) The method according to any one of features (1)-(8), in which thedetermining whether the block is partitioned in accordance with thenon-uniform quad split partition type further includes: determining asize of the block along an edge perpendicular to a direction in whichthe block is partitioned, and in response to determining that the sizeof the block along the edge perpendicular to the direction in which theblock is partitioned is greater than equal to 32 samples, determiningthat the block is partitioned in accordance with the non-uniform quadsplit partition type.

(10) The method according to any one of features (1)-(9), in which thedetermining whether the block is partitioned in accordance with thenon-uniform quad split partition type further includes: in response todetermining that a partition of the block in accordance with thenon-uniform quad split partition type results in at least one sub-blockbeing outside of a picture boundary of the current picture, determiningthat the block is not partitioned in accordance with the non-uniformquad split partition type.

(11) A video decoder for video decoding including processing circuitryconfigured to: acquire a current picture from a coded video bitstream,retrieve signaling information from the coded video bitstream for ablock in the current picture, determine, from the signaling information,whether the block is partitioned in accordance with a quad splitpartition type, in response to the determination that the block is notpartitioned in accordance with the quad split partition type, determinewhether the block is partitioned in accordance with a split partitiontype, in response to the determination that the block is partitioned inaccordance with the split partition type, determine whether the block ispartitioned in accordance with a non-uniform quad split partition typein which the block is partitioned into four sub-blocks along a samedirection, and in response to the determination that the block ispartitioned in accordance with the non-uniform quad split partitiontype, reconstruct the block in accordance with the non-uniform quadsplit partition type.

(12) The video decoder according to feature (11), in which thedetermination whether the block is partitioned in accordance with thenon-uniform quad split partition type further includes the processingcircuitry configured to: determine whether the block is partitioned inaccordance with one of (i) a binary split partition type in which theblock is partitioned into two sub-blocks along a same direction and (ii)a non-binary split partition type, and in response to the determinationthat the block is partitioned in accordance with the non-binary splitpartition type, determine whether the block is partitioned in accordancewith one of (i) a ternary split partition type in which the block ispartitioned into three sub-blocks along a same direction and (ii) thenon-uniform quad split partition type.

(13) The video decoder according to feature (11) or (12), in which thedetermination whether the block is partitioned in accordance with thenon-uniform quad split further includes the processing circuitryconfigured to: determine whether the block is partitioned in accordancewith one of (i) a non-quad split partition type, and (ii) thenon-uniform quad split partition type.

(14) The video decoder according to any one of features (11)-(13), inwhich response to the determination that the block is partitioned inaccordance with the non-quad partition type, the processing circuitry isfurther configured to determine whether the block is partitioned inaccordance with one of (i) a binary split partition type in which theblock is partitioned into two sub-blocks along a same direction and (ii)a ternary split partition type in which the block is partitioned intothree sub-blocks along a same direction.

(15) The video decoder according to any one of features (11)-(14), inwhich the block partitioned in accordance with the non-uniform quadpartition split type includes first and second sub-blocks of a samefixed size, a third sub-block that is twice the fixed size, and fourthsub-block that is four times the fixed size.

(16) The video decoder according to feature (15), in which the first andsecond sub-blocks are adjacent to each other.

(17) The video decoder according to feature (15), in which the first andsecond blocks are not adjacent to each other.

(18) The video decoder according to any one of features (11)-(17), inwhich the determination whether the block is partitioned in accordancewith the non-uniform quad split partition type further includes theprocessing circuitry configured to: determine a size of the block alongan edge perpendicular to a direction in which the block is partitioned,and in response to the determination that the size of the block alongthe edge perpendicular to the direction in which the block ispartitioned is greater than equal to 32 samples, determine that theblock is partitioned in accordance with the non-uniform quad splitpartition type.

(19) The video decoder according to any one of features (11)-(18),wherein the determination whether the block is partitioned in accordancewith the non-uniform quad split partition type further includes theprocessing circuitry further configured to: in response to thedetermination that a partition of the block in accordance with thenon-uniform quad split partition type results in at least one sub-blockbeing outside of a picture boundary of the current picture, determinethat the block is not partitioned in accordance with the non-uniformquad split partition type.

(20) A non-transitory computer readable medium having instructionsstored therein, which when executed by a processor in a decoder causesthe processor to executed a method including acquiring a current picturefrom a coded video bitstream; retrieving signaling information from thecoded video bitstream for a block in the current picture; determining,from the signaling information, whether the block is partitioned inaccordance with a quad split partition type; in response to determiningthat the block is not partitioned in accordance with the quad splitpartition type, determining whether the block is partitioned inaccordance with a split partition type; in response to determining thatthe block is partitioned in accordance with the split partition type,determining whether the block is partitioned in accordance with anon-uniform quad split partition type in which the block is partitionedinto four sub-blocks along a same direction; and in response todetermining that the block is partitioned in accordance with thenon-uniform quad split partition type, reconstructing the block inaccordance with the non-uniform quad split partition type.

The invention claimed is:
 1. A method of video decoding for a decoder,the method comprising: acquiring a current picture from a coded videobitstream; retrieving signaling information from the coded videobitstream for a block in the current picture; determining, from thesignaling information, whether the block is partitioned in accordancewith a quad split partition type; in response to determining that theblock is not partitioned in accordance with the quad split partitiontype, determining whether the block is partitioned in accordance with asplit partition type; in response to determining that the block ispartitioned in accordance with the split partition type, determiningwhether the block is partitioned in accordance with a non-uniform quadsplit partition type of a plurality of non-uniform partition types inwhich the block consists of four sub-blocks along a same direction; andin response to determining that the block is partitioned in accordancewith the non-uniform quad split partition type, reconstructing the blockin accordance with the non-uniform quad split partition type of theplurality of non-uniform partition types, wherein the block partitionedin accordance with the non-uniform quad partition split type includesfirst and second sub-blocks of a same fixed size, a third sub-block thatis twice the fixed size, and a fourth sub-block that is four times thefixed size.
 2. The method of according to claim 1, wherein thedetermining whether the block is partitioned in accordance with thenon-uniform quad split partition type further includes: determiningwhether the block is partitioned in accordance with one of (i) a binarysplit partition type in which the block is partitioned into twosub-blocks along a same direction and (ii) a non-binary split partitiontype, and in response to determining that the block is partitioned inaccordance with the non-binary split partition type, determining whetherthe block is partitioned in accordance with one of (i) a ternary splitpartition type in which the block is partitioned into three sub-blocksalong a same direction and (ii) the non-uniform quad split partitiontype.
 3. The method according to claim 1, wherein the determiningwhether the block is partitioned in accordance with the non-uniform quadsplit further includes: determining whether the block is partitioned inaccordance with (i) a non-quad split partition type, and (ii) thenon-uniform quad split partition type.
 4. The method of according toclaim 3, wherein in response to determining that the block ispartitioned in accordance with the non-quad partition type, determiningwhether the block is partitioned in accordance with one of (i) a binarysplit partition type in which the block is partitioned into twosub-blocks along a same direction and (ii) a ternary split partitiontype in which the block is partitioned into three sub-blocks along asame direction.
 5. The method according to claim 1, wherein the firstand second sub-blocks are adjacent to each other.
 6. The methodaccording to claim 1, wherein the first and second sub-blocks are notadjacent to each other.
 7. The method according to claim 1, wherein thefirst sub-block is between the third sub-block and the fourth sub-block.8. The method according to claim 1, wherein the determining whether theblock is partitioned in accordance with the non-uniform quad splitpartition type further includes: determining a size of the block alongan edge perpendicular to a direction in which the block is partitioned,and in response to determining that the size of the block along the edgeperpendicular to the direction in which the block is partitioned isgreater than equal to 32 samples, determining that the block ispartitioned in accordance with the non-uniform quad split partitiontype.
 9. The method according to claim 1, wherein the determiningwhether the block is partitioned in accordance with the non-uniform quadsplit partition type further includes: in response to determining that apartition of the block in accordance with the non-uniform quad splitpartition type results in at least one sub-block being outside of apicture boundary of the current picture, determining that the block isnot partitioned in accordance with the non-uniform quad split partitiontype.
 10. A video decoder for video decoding, comprising: processingcircuitry to: acquire a current picture from a coded video bitstream,retrieve signaling information from the coded video bitstream for ablock in the current picture, determine, from the signaling information,whether the block is partitioned in accordance with a quad splitpartition type, in response to the determination that the block is notpartitioned in accordance with the quad split partition type, determinewhether the block is partitioned in accordance with a split partitiontype, in response to the determination that the block is partitioned inaccordance with the split partition type, determine whether the block ispartitioned in accordance with a non-uniform quad split partition typeof a plurality of non-uniform partition types in which the blockconsists of four sub-blocks along a same direction, and in response tothe determination that the block is partitioned in accordance with thenon-uniform quad split partition type, reconstruct the block inaccordance with the non-uniform quad split partition type of theplurality of non-uniform partition types, wherein the block partitionedin accordance with the non-uniform quad partition split type includesfirst and second sub-blocks of a same fixed size, a third sub-block thatis twice the fixed size, and a fourth sub-block that is four times thefixed size.
 11. The video decoder according to claim 10, wherein thedetermination whether the block is partitioned in accordance with thenon-uniform quad split partition type further includes the processingcircuitry configured to: determine whether the block is partitioned inaccordance with one of (i) a binary split partition type in which theblock is partitioned into two sub-blocks along a same direction and (ii)a non-binary split partition type, and in response to the determinationthat the block is partitioned in accordance with the non-binary splitpartition type, determine whether the block is partitioned in accordancewith one of (i) a ternary split partition type in which the block ispartitioned into three sub-blocks along a same direction and (ii) thenon-uniform quad split partition type.
 12. The video decoder accordingto claim 10, wherein the determination whether the block is partitionedin accordance with the non-uniform quad split further includes theprocessing circuitry configured to: determine whether the block ispartitioned in accordance with (i) a non-quad split partition type, and(ii) the non-uniform quad split partition type.
 13. The video decoderaccording to claim 12, wherein in response to the determination that theblock is partitioned in accordance with the non-quad partition type, theprocessing circuitry is further configured to determine whether theblock is partitioned in accordance with one of (i) a binary splitpartition type in which the block is partitioned into two sub-blocksalong a same direction and (ii) a ternary split partition type in whichthe block is partitioned into three sub-blocks along a same direction.14. The video decoder according to claim 10, wherein the first andsecond sub-blocks are adjacent to each other.
 15. The video decoderaccording to claim 10, wherein the first and second sub-blocks are notadjacent to each other.
 16. The video decoder according to claim 10,wherein the determination whether the block is partitioned in accordancewith the non-uniform quad split partition type further includes theprocessing circuitry configured to: determine a size of the block alongan edge perpendicular to a direction in which the block is partitioned,and in response to the determination that the size of the block alongthe edge perpendicular to the direction in which the block ispartitioned is greater than equal to 32 samples, determine that theblock is partitioned in accordance with the non-uniform quad splitpartition type.
 17. The video decoder according to claim 10, wherein thedetermination whether the block is partitioned in accordance with thenon-uniform quad split partition type further includes the processingcircuitry further configured to: in response to the determination that apartition of the block in accordance with the non-uniform quad splitpartition type results in at least one sub-block being outside of apicture boundary of the current picture, determine that the block is notpartitioned in accordance with the non-uniform quad split partitiontype.
 18. A non-transitory computer readable medium having instructionsstored therein, which when executed by a processor in a decoder causesthe processor to execute a method comprising: acquiring a currentpicture from a coded video bitstream; retrieving signaling informationfrom the coded video bitstream for a block in the current picture;determining, from the signaling information, whether the block ispartitioned in accordance with a quad split partition type; in responseto determining that the block is not partitioned in accordance with thequad split partition type, determining whether the block is partitionedin accordance with a split partition type; in response to determiningthat the block is partitioned in accordance with the split partitiontype, determining whether the block is partitioned in accordance with anon-uniform quad split partition type of a plurality of non-uniformpartition types in which the block consists of four sub-blocks along asame direction; and in response to determining that the block ispartitioned in accordance with the non-uniform quad split partitiontype, reconstructing the block in accordance with the non-uniform quadsplit partition type of the plurality of non-uniform partition types,wherein the block partitioned in accordance with the non-uniform quadpartition split type includes first and second sub-blocks of a samefixed size, a third sub-block that is twice the fixed size, and a fourthsub-block that is four times the fixed size.